I agree that you should look at when this bad behavior started in comparison to when you and their father split up... if the two go hand in hand then some family counseling may be in order to bring some peace and love back into the home.

... I am thinking of a few ladies I know that have young children the same age as your kids and the one family that stands out is of a lady that failed to put discipline into her children's life at a young age because dad had left them and she over compensated for that by lacking proper discipline they needed.
>>>> is this possibly the case with your kids? (just asking so I can try to help)